Upholstery fabrics made from wool are known to have an attractive appearance and feel to the touch. Due to the tendency of wool to shrink after washing in water, however, attempts have been made to substitute wool fabrics with fabrics made from synthetic materials such as polyester. The appearance and feel of fabrics made from synthetic materials, however, has been found to be inferior to that of fabrics made from wool. Fabrics made from blends of wool fibers with certain synthetic fibers retain some of the aesthetic features of wool as well as some of the cost benefits and potential property advantages of synthetics.
In the aircraft industry, seat cover fabrics are subject to specifications provided by aircraft manufacturers such as Airbus and Boeing. The relevant Airbus technical specification, for example, is TL 25/5092/83. The relevant flammability, smoke and toxicity portions of the standard are FAR 25.853 (b), appendix F, amended 32, JAR 25853 (b), appendix change 10, and ABD 0031 (previously numbered ATS 1000.001). These specifications include standards for abrasion resistance including resistance to abrasion simulated by a Martindale tester. Resistance to stains resulting from spills, and to loss of color and shrinkage due to washing, is also specified. Seat cover fabrics may be required to meet specifications after a minimum of 10 washings. An areal weight below 470 g/m2 is specified. It is desirable that shrinkage during service life, including shrinkage due to cleaning processes, be minimized. Resistance to pilling, corrosion and color loss may also be specified.
The relevant Boeing specification is BMS 8-236, for general upholstery interior applications. The flammability standard is provided by BSS7230, a twelve second vertical burn test, in which the sample is required to self extinguish within fifteen seconds, with a burn length of less than eight inches. Drips, if any, are required to extinguish in less than five seconds. Smoke emissions of less than 200 are specified according to BSS7238. Prescribed limits for individual toxic components in toxic gas emissions are tested according to BSS 7239. Dimensional stability is evaluated after prescribed cleaning, whether dry cleaning or water washing methods are used. While zero shrinkage is ideal, shrinkage levels of less than 6%, in both warp and fill directions, are acceptable. Standards for appearance, snag resistance, pilling resistance, color fastness and strength are part of the overall specification.
Wool fabrics are typically cleaned using a dry-cleaning process, including immersion in a solvent such as perchloroethylene, in order to maintain the dimensional stability of the fabric. Due to environmental and cost considerations, it would be desirable to clean wool-based fabrics without the use of perchloroethylene or other organic solvents. Water containing surfactants or detergents is highly effective in cleaning such fabrics, however, use of water-based cleaning solutions has been limited by the tendency of wool based fabrics to shrink after being subjected to such solutions. Synthetic fibers, on the other hand, are typically highly resistant to shrinkage following washing in water. Synthetic fibers, however, tend to be highly flammable.
Because of the nature of the constituent parts of the above mentioned wool-synthetic blends, such blends in the prior art are typically neither flame resistant, nor shrink resistant when washed in water. There is a need for fabrics made from wool-synthetic blends that will meet the special requirements for aircraft interiors.